As a prior art slide rail device for vehicle, a device is known which is equipped with a left and right pair of lower rails which include a plurality of convex teeth (lock teeth) extending and arranged in a forward/rearward direction and which are fixed to a vehicle interior floor, a left and right pair of upper rails which support the seating portion of a seat and are slidably supported by the left and right pair of lower rails, locking levers which are accommodated in the internal spaces of the upper rails and which are supported by the upper rails to be rotatable in the vertical direction between a lock position to be engaged with the aforementioned convex teeth and an unlock position to release the engagement with the convex teeth, wire springs (biaser) which bias and rotate the locking levers toward the lock position, and an operating lever, the rear end of which is fixed to the locking levers and the front end of which projects toward the front of the upper rails.
Therefore, when an occupant applies no operating force to the operating lever, the slide positions of the seat and the upper rails with respect to the lower rails are maintained since the lock levers which are held in the lock position by the wire springs are engaged with some of the convex teeth. On the other hand, upon a passenger operating the operating lever to rotate the lock levers to the unlock position against the biasing force of the wire springs, the lock levers are disengaged from the convex teeth to thereby allow the seat and the upper rails to slide with respect to the lower rails.